Recently, with advances in digital technology, electronic devices, such as portable information devices and home information appliances, have been developed to provide higher functionality. As the electronic devices have been developed to provide higher functionality, miniaturization and an increase in speed of semiconductor elements for use with the electronic devices are making rapid progress. Among them, the use of large-capacity nonvolatile memory devices which are typified by a flash memory has been expanding at a rapid pace. Furthermore, as next-generation nonvolatile memory devices that can replace the flash memory, research and development is advancing on a nonvolatile memory device including a variable resistance nonvolatile memory element, which includes a variable resistance layer having a resistance value that changes reversibly in response to electric signals.
Materials used as variable resistance layers are divided into two general types. One type of materials are oxides of transition metals (Ni, Nb, Ti, Zr, Hf, Co, Fe, Cu, Cr, and the like) disclosed in Patent Literature (PTL) 1 and Non Patent Literature (NPL) 1 to 3, and in particular is an oxide in which an oxygen content atomic percentage is deficient in terms of stoichiometric composition (hereafter referred to as an oxygen-deficient oxide). The other type of materials is perovskite materials (Pr(1-x)CaxMnO3 (PCMO), LaSrMnO3 (LSMO), GdBaCoxOy (GBCO), and the like).
Furthermore, PTL 2 and 3 disclose a nonvolatile memory element which can, when the latter type that is perovskite material is used as the variable resistance layer, store not only two values (two states, namely, a low resistance state and a high resistance state) but multiple values of three or more values.